散式和聚式流态化的直接数值模拟——EMMS模型稳定性条件的验证
文献类型：学位论文
| 作者 | 魏民 |
| 学位类别 | 硕士 |
| 答辩日期 | 2012-05-29 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 李静海 ; 王利民 |
| 关键词 | 直接数值模拟 流态化 能量最小多尺度 时驱硬球 格子玻尔兹曼方法 |
| 其他题名 | Direct Numerical Simulation of Particulate and Aggregative Fluidization―Verification of Stability Condition of the EMMS Model |
| 学位专业 | 化学工程 |
| 中文摘要 | 流态化系统是典型的非平衡系统，呈现出时空多尺度结构。因此，描述该体系的模型必然应符合多尺度思想。能量最小多尺度(EMMS)模型考虑了系统的非均匀结构特性，能够较好地描述稀、密两相流中非均匀流动结构的时均行为特征，在气固循环流态化中得到广泛的应用。建立EMMS模型时，为了能够封闭求解，引入了系统的稳定性条件，即流体用于悬浮和输送单位质量固体颗粒消耗的能量最小的假设。本文的主要研究目标是利用高可信度的数值方法对这一稳定性条件进行验证，并深入探讨了非均匀结构形成的机理。第1章综述了散式流态化和聚式流态化判据方面的研究成果，以及流态化数值模拟领域的主要方法，分析了采用数值模拟方法研究流态化机理问题的必要性和可行性。简要回顾了散式流态化和聚式流态化统一问题的研究工作。第2章详细介绍了本论文所采用的数值计算方法—时驱硬球格子玻尔兹曼(TDHS-LBM)方法，包括流场求解、颗粒运动处理以及流固耦合方式，并对该方法进行了数值验证，验证了其合理性和有效性。第3章阐明了EMMS模型的物理模型和计算框架。鉴于采用原始EMMS模型在处理能耗分解问题上的难度，本论文采用从EMMS模型上发展起来并适用于鼓泡床体系的EMMS/bubbling模型进行能耗分解。提出了能耗量化方法，为稳定性条件的验证奠定了基础。第4章对散式流态化和聚式流态化体系进行了数值模拟，成功复现了两类流态化体系中的典型现象。通过对流态化系统中能量耗散的统计，发现EMMS模型稳定性条件在散式流态化和聚式流态化中均适用。进一步分析发现，聚式流态化中 的值远小于散式流态化，并且聚式流态化比散式流态化更快地达到动态稳定的状态，这一点可以作为散式流态化和聚式流态化的判据之一。最后，第5章对本论文进行了总结并对未来工作进行了展望。 |
| 英文摘要 | Fluidization systems are typical non-equilibrium systems, featuring spatio-temporal multi-scale structures. Therefore, the model for description of the systems should be consistent with the concept of multi-scale. The Energy-Minimization Multi-Scale (EMMS) model, taking the heterogeneous structure into account, has been applied in gas-solid circulating fluidization systems due to its capability in predicting the time-averaged characteristics of the dilute and dense phases. When establishing the EMMS model, the stability condition, , was introduced in order to close the equations. The main objective of this study is to verify the stability condition by a high-fidelity numerical method, and further to explore its effect on heterogeneous structures. Chapter 1 reviews the criteria for distinguishing particulate from aggregative fluidization and the numerical methods for simulation of fluidization. Then, we explain and elaborate on the necessity and the feasibility of direct numerical simulation for studying fluidization. The chapter also reviews the research work focusing on the unification of particulate and aggregative fluidization systems. In chapter 2, a computation scheme coupled time-driven hard-sphere and lattice Boltzmann method (TDHS-LBM) is introduced in detail, including the solver for the continuous fluid, particle movement process, particle-fluid coupling, and some examples are simulated to validate the method. In chapter 3, the physical model and computational framework of EMMS model are elaborated to analyze the energy consumption in fluidization systems. Due to the difficulty to calculate the energy consumption by the original EMMS, EMMS/bubbling model is used to investigate bubbling bed system. The statistical method of energy consumption is defined to verify the stability condition. In chapter 4, particulate and aggregative fluidization systems are simulated successfully with the TDHS-LBM method which reproduce some typical phenomena in fluidization systems. By analysing the results of energy consumption, the stability condition in the EMMS model is verified to hold both in particulate and aggregative fluidization systems. Further work shows that the value of in aggregative fluidization is much lower than that in particulate fluidization. Analysis of direct simulation results also shows that the process approaching the steady state in aggregative fluidization is much faster than that in particulate one, which can be taken into account in distinguishing particulate and aggregative fluidization. Finally, chapter 5 summarizes the main results in this thesis, and discusses some future directions on direct numerical simulation and its applications to fluidization. |
| 语种 | 中文 |
| 公开日期 | 2013-09-25 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1813]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 魏民. 散式和聚式流态化的直接数值模拟——EMMS模型稳定性条件的验证[D]. 中国科学院研究生院. 2012. |
入库方式： OAI收割
来源：过程工程研究所
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